Some belated updates

Haven't touched this project in a while.

I learned a few skills from the last GGJ, so I thought I'd give this thing a slight update. Some things I've been wanting to add for a long while now.

  * Added a high score list. Right now actually getting on it is probably still buggy. I'm still thinking of how I want to implement this. It  will be a TBD priority for this project.

 * Added extra lives. The game will be much easier to go up. Also added a second fuel powerup. It adds much more fuel than the other. I'll likely move them to a different place on the hud next update.

I still want to add better explosions and actual levels and an ending. Will also implement an endless mode too, and adjust the final scores accordingly.